This study presents the development of super-tough carbon-nanotube (CNT) composite fibres that are tougher than any natural or synthetic organic fibre. These fibres are produced using a modified coagulation-based spinning method, which allows for the continuous production of 100-metre-long solid CNT composite fibres at a rate of over 70 cm min⁻¹. The fibres have a diameter of about 50 μm and contain around 60% SWNTs by weight, with a tensile strength of 1.8 GPa, matching that of spider silk. They exhibit a toughness that is seven times greater than previously reported coagulation-spun nanotube fibres and over 10⁴ times higher than 'dry-spun' carbon-nanotube fibres. The toughness is attributed to a combination of high strength and high strain to failure. Although the Young's modulus of the fibres is lower than that of high-performance graphite fibres or individual SWNTs, their normalized values are more than twice those of steel wire. The fibres are also 20 times as tough as steel wire. The toughness is achieved due to the absence of measurable fibre necking during deformation, suggesting a newtonian flow behavior. The fibres are used to make supercapacitors that can be woven into textiles, offering promising applications in electronic textiles such as distributed sensors, electronic interconnects, electromagnetic shields, antennas, and batteries. The fibres are easy to weave and sew, making them suitable for various electronic-textile applications. The study highlights the potential of these CNT composite fibres for future electronic textiles and their superior mechanical properties compared to existing materials.This study presents the development of super-tough carbon-nanotube (CNT) composite fibres that are tougher than any natural or synthetic organic fibre. These fibres are produced using a modified coagulation-based spinning method, which allows for the continuous production of 100-metre-long solid CNT composite fibres at a rate of over 70 cm min⁻¹. The fibres have a diameter of about 50 μm and contain around 60% SWNTs by weight, with a tensile strength of 1.8 GPa, matching that of spider silk. They exhibit a toughness that is seven times greater than previously reported coagulation-spun nanotube fibres and over 10⁴ times higher than 'dry-spun' carbon-nanotube fibres. The toughness is attributed to a combination of high strength and high strain to failure. Although the Young's modulus of the fibres is lower than that of high-performance graphite fibres or individual SWNTs, their normalized values are more than twice those of steel wire. The fibres are also 20 times as tough as steel wire. The toughness is achieved due to the absence of measurable fibre necking during deformation, suggesting a newtonian flow behavior. The fibres are used to make supercapacitors that can be woven into textiles, offering promising applications in electronic textiles such as distributed sensors, electronic interconnects, electromagnetic shields, antennas, and batteries. The fibres are easy to weave and sew, making them suitable for various electronic-textile applications. The study highlights the potential of these CNT composite fibres for future electronic textiles and their superior mechanical properties compared to existing materials.